The present invention relates to a method and apparatus for wrapping a load with packaging material.
Loads have been stretch wrapped with stretch wrap packaging material by securing a leading end of the packaging material to the load or a turntable clamp, dispensing the packaging material by providing relative rotation between the load and a packaging material dispenser to cause the load to be enveloped by the packaging material, and severing the packaging material between the load and a packaging material dispenser. The relative rotation between the load and the dispenser can be provided either by rotating the load on a turntable, or by rotating the dispenser around a stationary load. Stretch wrapping usually employs a web of stretch film as the packaging material, and the machinery can be either automatic or semi-automatic.
Semi-automatic stretch wrapping machinery requires the operator to attach a leading end of the packaging material to the load for each load to be wrapped. This is typically accomplished by forming a rope in the leading end of the film and then inserting this end between the layers of the load or by tying the end of the packaging material to the edge of the supporting wood pallet or any suitable outcropping on the load. This attachment must be relatively strong since it provides the reaction to force needed to pull the film from the film dispenser during the initiation of the relative rotation between the load and the film dispenser. The attachment or tying of the film makes film removal more difficult after the load has been shipped to its destination.
Automatic stretch wrapping machines are significantly more expensive than semi-automatic machines. The automatic machines typically use film clamps that grip the film web between two opposed surfaces, use electrical or pneumatic actuators to open and close the clamps, typically supply electrical or pneumatic power to the actuators on a turntable through the journal of the turntable, and use hot wires or other expensive cutting devices to cut the film. Such film clamps create a “tenting” effect during wrapping due to the distance between the clamp and the load during wrapping, resulting in wasted film and loosely wrapped loads.
In light of the cost of such automatic machines, there is a need for a method and apparatus for wrapping a load with packaging material that operates as effectively as those previously developed to allow automatic release and clamping of portions of the packaging material but which can be manufactured at a lower cost.